Author(s)

V Fuis & P Janícek

Abstract

Today, the problem of reliability of the hip joint ceramic heads becomes important, since world-wide the destruction of the ceramic head has generally been stated in a non-negligible number of patients. Therefore stress and reliability analyses of the ceramic heads were made using experimental and computational modelling aimed at finding the causes of the head destruction. The deformation and stresses are obtained by computational methods (finite elements) under testing conditions, in accordance with IS0 7206-5. Head reliability is based on the Weibull weakest link theory. The head's stress and reliability are significantly influenced by manufacturing inaccuracies of the cone contact areas. The considered manufacturing inaccuracies are modelled as axisymmetric or 3D. The effects of manufacturing inaccuracies on the head's hoop stress and the head's contact pressure along the contact taper are analysed in detail, because the maximum tensile stress acts in this region. Finally, the effect of the mentioned manufacturing inaccuracies on the head's failure probability during the loading is shown. The results obtained are used in clinical practice and in the technological processes of stem and ceramic head manufacturing. 1 Introduction One of the most frequently operated joints of the human body is the hip joint. In young patients, the operation is mostly aimed at reconstructing the joint's pathologically developed geometry. In older age, operations prevail in which the

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